1. Field of the Invention
The present invention relates to a sheet eject device, a fullness detecting method, and a computer-readable recording medium.
2. Description of the Related Art
In recent years, technologies relevant to multifunction peripherals (MFP) have advanced. For example, CPUs have become high performance, memories have become high capacity, communications have become high speed, and digital images have become high quality. Accordingly, in addition to functioning merely as a digital copier, an MFP may have various functions such as a fax machine, a printer, and a scanner connected to a network, and may be used in various situations in the user's environment.
An image forming apparatus such as a printer or an MFP as described above includes sheet eject trays for holding sheets that are ejected after undergoing a printing operation. A sheet that is ejected from a sheet eject outlet is held on this sheet eject tray until a user comes to collect it. A sheet eject tray is usually positioned below the sheet eject outlet of the main body of the MFP. Accordingly, if sheets are continuously ejected, the sheet eject outlet may be blocked. Thus, the number of sheets that can be held on the sheet eject tray is limited. If the sheet eject outlet becomes blocked as sheets are continuously ejected and accumulated on the sheet eject tray, no more sheets can be ejected, and a paper jam occurs near the sheet eject outlet.
Conventionally, as a method of preventing such a paper jam from occurring, a sensor is provided near the sheet eject outlet for detecting whether the sheet eject tray is filled with sheets. When it is detected that the sheet eject tray is filled with sheets (when sheet fullness is detected), the printing/sheet ejecting process of the MFP is temporarily stopped.
Furthermore, there are cases where the sheet eject tray of the MFP can be moved up and down. In this case, when sheet fullness is detected (when it is detected that the sheet eject tray is filled with ejected sheets), the sheet eject tray is moved down to temporarily increase the number of sheets that can be held on the sheet eject tray. Accordingly, a paper jam is prevented from occurring.
Furthermore, there are cases where the MFP is provided with plural sheet eject trays. For example, it is assumed that the MFP has two sheet eject trays provided one above the other. In this case, even when the bottom sheet eject tray is specified, when the fullness detecting sensor detects that the bottom sheet eject tray is filled with sheets, a control operation is performed so that the sheets are ejected to the top sheet eject tray. Accordingly, a paper jam is prevented from occurring.
As a relevant technology, patent document 1 discloses an invention in which an eject sensor and fullness detection sensor are implemented by a common component. The movement of a filler used for detection is devised so that the component operates as an eject sensor under regular conditions, and when the sheet eject tray is filled with sheets and the angle of the filler changes, the component operates as a fullness detection sensor.
However, in the conventional technology, the fullness detection sensor is implemented by a physical mechanism. Therefore, there have been various issues in applying the fullness detection sensor to a low-cost, slim-type MFP. For example, the fullness detection sensor requires component costs and mounting costs, which are disadvantageous in terms of achieving a low-cost machine. Furthermore, the fullness detection sensor is mounted as a physical mechanism, and therefore a predetermined space is required in the MFP main unit for providing the fullness detection sensor including an operating part and a sensor part. In order to achieve a slim-type machine, even such a small space is preferably reduced.
In the invention of patent document 1, the eject sensor and the fullness detection sensor are implemented by a common component, and therefore it is unnecessary to provide an additional fullness detection sensor. Accordingly, costs and space can be reduced in this respect. However, the filler used in the sensor of the invention of patent document 1 is larger than that of a conventional sensor used only for detecting ejection. In this respect, the cost and space of the eject sensor is increased in the invention of patent document 1.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2003-192225